It is well known in the oil and gas extraction industry that well stimulus by the injection of fluid suspended sands at high pressures down a drill hole results in improved hydrocarbon production. This process is commonly known as “frac-ing” and the sand used is called a proppant or “frac sand”. Silica is most often used as a frac sand because of physical and chemical properties that resists crushing and chemical attack. The amount of sand proppant used in a typical deep well frac-ing operation ranges from 30,000 lbs to 50,000 lbs. In specific well fields the amount of frac sand used in a single day may reach 1.5 million pounds. Therefore, frac sand management techniques are becoming increasingly important in hydrocarbon recovery operations because proppant represents a significant industrial waste stream. When these materials are transported back to facilities with crude oil from the wells, the beads settle out, along with formation sand, to form a semi-solid sludge in the bottoms of vessels. This proppant/frac sand often goes into lined landfills creating a significant storage and pollution problem. Separating the proppant from the oil or oil-waste has a number of advantages including recovery of a reusable product, reduction of waste storage costs and mitigation of toxic waste pollution. Major hydrocarbon producers are under increasing public and regulatory pressure to conduct their businesses in a manner that is as environmentally benign as possible. This has created a problem that was heretofore addressed by burying the mixtures. Since, burying or long-term storage is not longer a feasible solution, there has been created an imperative to resolve this issue.
This problem was partially solved by my invention entitled “Treatment of Oil, Water and Sand Mixtures” described in my Canadian Patent Pending 2,196,522. This invention describes a method and apparatus for treating oil, water and sand mixtures to separate components. However, this invention was designed to be stationary. Due to the remote nature of many oil and gas well fields, trucking oil, water and sand mixtures to a separation plant is prohibitively expensive.
Attempts have been made to design mobile systems for separate components of oil, water and sand mixtures. For example, U.S. Pat. No. 4,929,353 entitled “Portable Liquid-Solid Separator for Bulk Sludge” issued to Harris on May 29, 1990 and U.S. Pat. No. 6,110,383 entitled “Oil/Water Separator” issued to Coombs et al on Aug. 29, 2000 tries to resolve the problem of separating liquids from solids. However, these inventions do not provide means to separate a three-component system of oil, water and sand into cleansed and recyclable constituent parts. Furthermore, these inventions do not address the need to interface the separators with storage vessels holding the mixtures. As well, these inventions are not self-contained and rely upon external sources of water that may not be available at remote storage sites.
Therefore, there continues to be a need, not heretofore known in the prior art, of a self-contained mobile system for dewatering formation sand from hydrocarbon production stored a distant and remote locations.